Wow, this is fantastic stuff. Thanks for the explanations too- I've been doing Ruby/Python for awhile now, but I've always wanted to move more into Frontend Dev work, and I found a lot of this helpful.
Does anyone know of a list like this for other types of developers? Like a back-end development position etc. I really also like the link out to the Github page with a much more extensive list of questions.
I usually bring printed code samples to interviews and have others on my web site in case they are interested. I am not sure it ever helped me get a job, but it probably didn't hurt.